Electrosurgery is a form of surgery in which body tissue is cut or cauterized by a high frequency current. A variety of electrosurgical tools have been employed. In monopolar adaptations, a radio frequency (RF) signal is transmitted to an electrosurgical electrode. When employing this type of electrosurgical device, a "patient plate" is placed upon the patient's skin outside of the surgical field, with the plate being connected back to the RF signal generator to ground the patient. The current from the generator thus completes its circuit when the electrode of the electrosurgical device comes close to or in contact with the patient's body. The small point of approach or contact between the body and the electrosurgical device creates an intense current localized so that a cutting action may occur. Since the contact area between the patient and the patient plate is so large, the current is not localized and the current flow does not harm the patient.
In bipolar adaptations, an RF generator transmits current to an electrosurgical device that contains two electrodes one of which conducts the current back to the generator to complete the circuit. A small gap exists between the two conductive elements in the device between which the current flows. The flowing current between the two electrodes provides the heat for cutting or for coagulation of bleeding sites.
The electrosurgical electrode has been maintained for many years in a wide variety of shapes such as needles for delicate cutting, or a wire loop for scraping. In addition, electrosurgical electrodes shaped as spatulas have been used in normal surgical cutting like a scalpel. Although most electrosurgical electrodes are composed of stainless steel, some are composed of alloys containing primarily tungsten, molybdenum, chromium, nickel or cobalt.
When in a cutting mode, the current created when a conventional electrosurgical electrode touches the body tissue incises the tissue. The heat created by the current occasionally penetrates deeply enough into the adjoining tissue so as to cause delayed healing and excessive scar formation. By varying the mode of the RF generator output, it is also possible to utilize the electrosurgical device to enhance cauterization or coagulation of blood in a wound. In the cauterizing mode, the electrosurgical electrode generates much more heat than when in the cutting mode.
Although offering certain advantages to conventional knife dissection, electrosurgical devices currently available suffer from several drawbacks. The relatively high current required causes occasional "sparking" of the current between the electrode and the body tissue when in the cutting mode. Such action causes localized hot spots that tend to smoke and give off a strong odor, as well as to create unnecessary tissue damage. When used in the cauterization mode, the high power required can often generate enough heat to melt the tip of stainless steel needle electrodes and destroy its sharpness.
U.S. Pat. Nos. 4,688,569 of Rabinowitz and 4,545,375 of Cline both describe monopolar electrosurgical electrode holder devices. Both of these contemplate the use of electrode needles for cutting and cauterizing and suggest the use of tungsten needles. The tungsten needles of these patents are machined and do not have the highly beneficial ultra-sharp tip of the present invention. U.S. Pat. No. 3,768,482 of Shaw describes a bipolar electrosurgical device resembling a scalpel.
This invention relates to an improved electrosurgical electrode and methods for utilizing and producing such superior electrosurgical electrodes. The invention encompasses the use of an "ultra-sharp" refractory alloy needle as an electrosurgical electrode, the method for manufacturing such device as well as the actual ultra-sharp needle itself.
Although ultra-sharp refractory alloy needles are known in the prior art, particularly in the field of electron microscopy, the surprising benefits obtained when employed as an electrosurgical electrode were quite unanticipated. Use of the ultra-sharp needle as an electrosurgical electrode allows for the use of a reduced power RF current due to the concentration of energy at the ultra-sharp tip. Efficient cutting at lower power reduces blood loss and leads to much cleaner and less traumatic cuts, resulting in less scar tissue. Use of the ultra-sharp needle also eliminates the drag when cutting tissue. This "no-touch" technique allows the surgeon a sensitive "feel", which is a significant benefit when performing extreme microsurgery. When used in the cauterization mode, the ultra-sharp electrode may again be used at relatively lower RF power, thereby eliminating problems associated with excessive heat, such as melting the electrode needle, and with greater control over the direction and location of sparking.
Ultra-sharp refractory alloy needles are traditionally produced in two manners. In the glass blowing art, clean tungsten alloy surfaces of wires and plates are produced by etching the tungsten surface by contacting the hot tungsten with a solid bed of sodium nitrite. The resulting oxidation reaction leaves the tungsten clean and bright. In the electron microscopy art, the ultra-sharp tungsten needle used for the electron source in the electron gun is also produced by placing a direct electrical anodic voltage on the tungsten and emersing it in a concentrated aqueous sodium hydroxide solution. The etching away of the tungsten surface can be manipulated to create the tapered ultra-sharp tungsten needle.
This invention describes a unique method for producing ultra-sharp tungsten alloy needles by reaction in a molten solution of sodium nitrite. By following the method taught by this invention, ultra-sharp needles are produced having superior consistency, symmetry, sharpness and tapering, ideal for practicing the electrosurgical methods of this invention.